As a apparatus for polishing a surface of a work such as a silicon wafer, a single-side polishing apparatus in which the work is polished by each face and a double-side polishing apparatus in which the both faces are polished at the same time.
A general single-side polishing apparatus comprises, as shown in FIG. 5, for example, a turn table 93 onto which a polishing pad 94 is attached, a polishing agent supply mechanism 96, a polishing head 92 and the like. In such a polishing apparatus 91, polishing is performed by holding a work W by the polishing head 92, supplying the polishing agent 95 onto the polishing pad 94 from the polishing agent supply mechanism 96, and rotating the turn table 93 and the polishing head 92, respectively, so as to bring the surface of the work W into sliding contact with the polishing pad 94.
As a method of holding the work on the polishing head, there is a method of attaching the work onto a flat disk-shaped plate through an adhesive such as a wax and the like. Other than that, particularly as a holding method of suppressing rise or sag of the work on its outer circumference portion and of improving flatness of the entire work, there is a so-called rubber-chuck method in which a work holding portion is made of a rubber film, a pressurized fluid such as air is poured into a back face of the rubber film, and the rubber film is inflated by a uniform pressure so as to press the work onto the polishing pad (See Japanese Unexamined Patent Publication (Kokai) No. H5-69310, for example).
An example of configuration of the prior-art rubber chuck polishing head is schematically shown in FIG. 4(a) and an enlarged diagram of a peripheral portion of the polishing head is shown in FIG. 4(b). An essential part of a polishing head 71 is a rigid ring 72 made of an annular SUS (stainless steel) and the like, a rubber film 73 bonded to the rigid ring 72, and a mid plate 74 joined to the rigid ring 72. A sealed space 75 is defined by the rigid ring 72, the rubber film 73, and the mid plate 74. Also, an annular template 76 is provided concentrically with the rigid ring 72 in the peripheral portion on a lower face part of the rubber film 73. Also, a through hole 78 for pressure adjustment communicating with a pressure adjustment mechanism 77 is provided at the center of the mid plate 74 so that a pressure of the space 75 is adjusted by supplying pressurized fluid by the pressure adjustment mechanism 77 and the like. Also, pressing means, not shown, for pressing the mid plate 74 in the direction of the polishing pad 94 is provided.
Using the polishing head configured as above, the work W is held on the lower face part of the rubber film 73 through a backing pad 79, an edge portion of the work W is held by the template 76, and the work W is brought into sliding contact with the polishing pad 94 attached onto an upper face of the turn table 93 by pressing the mid plate 74 for performing polishing.
By holding the work by the rubber film and polishing the work using the polishing head provided with the template as above, flatness (and polishing stock removal uniformity) of the entire work W is improved in some cases, but the flatness is still not favorable in other cases, and there is a problem that constant flatness can not be obtained stably.